A powertrain of an automobile or other vehicle generates power for delivery of motive force. In a conventional automobile, the powertrain often includes an internal combustion engine and a transmission. The powertrain may also be considered to include components of a vehicle driven by the engine and transmission, or drivetrain. The drivetrain of an automobile typically includes a drive shaft, one or more differentials, one or more axles, and wheels.
Hybrid vehicles use multiple sources of power to move the vehicle. The power sources typically combine an internal combustion engine and an electric motor system. The electric motor system often includes a set of batteries to drive one or more electric motors. An electric motor of a hybrid vehicle may be configured for operation as a generator during a regenerative braking mode to store energy in the batteries for later use.
Hybrid and other automobile vehicles are often configured with an internal combustion engine with a low number of cylinders. An engine with only a single cylinder (or other engines with few cylinders) may provide better fuel efficiency while remaining relatively simple and economical in construction.
Engines with few cylinders unfortunately exhibit large fluctuations in torque over each cycle of operation. The resulting output torque may have as high as 70% variation compared to its mean. The fluctuations in torque lead to large torsional vibrations that propagate through the powertrain. Devices are typically placed along the powertrain to absorb the torsional vibrations. For example, a flywheel or damper may be mounted on a drive shaft or placed at other locations along the kinematic chain of the vehicle.
Incorporation of the absorption devices undesirably increases the complexity of engines with few cylinders. Despite the increased complexity, the energy dissipated by the devices is nonetheless wasted.